The role of visual spatial attention in adult developmental dyslexia

Abstract

The present study investigated the nature of visual spatial attention deficits in adults with developmental dyslexia, using a partial report task with five-letter, digit, and symbol strings. Participants responded by a manual key press to one of nine alternatives, which included other characters in the string, allowing an assessment of position errors as well as intrusion errors. The results showed that the dyslexic adults performed significantly worse than age-matched controls with letter and digit strings but not with symbol strings. Both groups produced W-shaped serial position functions with letter and digit strings. The dyslexics' deficits with letter string stimuli were limited to position errors, specifically at the string-interior positions 2 and 4. These errors correlated with letter transposition reading errors (e.g., reading slat as “salt”), but not with the Rapid Automatized Naming (RAN) task. Overall, these results suggest that the dyslexic adults have a visual spatial attention deficit; however, the deficit does not reflect a reduced span in visual–spatial attention, but a deficit in processing a string of letters in parallel, probably due to difficulty in the coding of letter position.

Keywords:

• Visual spatial attention
• Developmental dyslexia
• String processing deficit
• Letter transpositions
• Crowding

Acknowledgments

During the preparation of this paper, Saskia Kohnen was supported by a Macquarie University Research Fellowship; Sachiko Kinoshita by a ARC Discovery Project grant (DP110100294). This work was supported by the Australian Research Council Centre of Excellence for Cognition and its Disorders (CE110001021).

Notes

¹In contrast to the W-shaped pattern found with letter and digits strings, for the symbol strings, Tydgat and Grainger (2009) found an inverted V-shaped function with no end-character advantage. We return to discuss this finding shortly.

²This would be the case for adult dyslexics. For young children with dyslexia with reduced experience with reading, the difference in the level of familiarity between letters and symbols may not be as great.